The present invention disclosed herein relates to a stretchable substrate, a stretchable photovoltaic apparatus, and a stretchable device. More particularly, the present invention relates to a technology of realizing a stretchable micro device array.
In recent years, there has been introduced a method of manufacturing an array system of electronic/photonic micro devices formed of an inorganic material having a stretchable property as well as a flexible property. Such an inorganic material includes materials such as single crystalline silicon and gallium arsenide. Meanwhile, in such devices and circuits, characteristics on the electric performance and reliability have been well established as a result of decades of study.
The existing flexible technologies or stretchable technologies have been focused on a hetero junction of an inorganic material and an organic material that have different elastic constants from each other so as to overcome a design limitation due to a platform which uses a traditional semiconductor element, for example, a semiconductor substrate having a planar shape, and hard and brittle properties.
A mechanical structure that isolates and protects a brittle inorganic material from a strain associated with a deformation occurring in other parts of the system is very important. This mechanical structure includes a specific means. The means may be exemplified by a structure that converts an out-of-plane of a mechanically buckled structure to a relative behavior such that the device is in-plane. An advanced approach based on such an idea has been introduced in non-patent document 1 suggested as a cited reference.
In the non-patent document 1, a study object is a mechanically structured substrate. In brief, a micro device is disposed on a protruded island. An interconnector interconnecting neighboring micro devices is curved and enters a trench isolating the islands from each other. By doing so, an upper surface of the island is not almost deformed and a boundary stress delivered to the micro device mounted on the upper surface of the island is minimized. Another advantage of the system introduced in the non-patent document 1 is an ability that may have a wide areal coverage where active devices performing a role such as photosensing or solar cell generation are placed in the entire two-dimensional range of the substrate.
By the non-patent document 1, effects that a stretchable characteristic for a micro device array is obtained and the areal coverage is increased may be obtained. However, when a strain corresponding to an extreme deformation condition is applied, the micro device array may be fractured. This is a cause shortening the life span of the stretchable device, and has a fatal influence on the reliability of the stretchable products that have to endure a continuous deformation behavior.